This application claims the priority of German Application No. 101 17 129.3, filed Apr. 6, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method of operating a generator for a vehicle, which generator is driven by an internal-combustion engine and supplies its energy to a vehicle wiring system.
In the case of conventional motor vehicles with internal-combustion engines, a current-generating generator is usually provided. The generator ensures a current supply to the electrical systems of the vehicle together with a storage battery. The generator is usually connected immediately after starting the internal-combustion engine in a ramp-shaped manner, that is, with an increasing load. The generator generates electric power which will be called upon as a function of the demand. It also charges a run-down storage battery.
However, particularly during a cold start of an internal-combustion engine, high emission values occur in the first operating phase of the internal-combustion engine, which high emission values are worsened by an immediate connection of the generator after the start of the internal-combustion engine. In the case of a known engine, when a battery is essentially completely charged, a generator supplies, for example, 1.5 kw of power. When the battery is in a poorly charged condition, or it is very aged, loads of up to 2.75 kw may occur.
It is an object of the present invention to improve the emission behavior of an internal-combustion engine shortly after its start.
This object is achieved by a method of operating a generator in a vehicle, which generator is driven by an internal-combustion engine and supplies its energy to a vehicle wiring system. The generator is operated immediately after the starting operation of the internal-combustion engine for a defined time period so as not to supply energy to the vehicle wiring system.
It is an important idea of the present invention to not additionally burden the internal-combustion engine with partially high generator outputs shortly after its starting. For this purpose, the generator is operated such that, for a defined time after the starting operation, it supplies essentially no energy to the electrical wiring.
According to a first embodiment of the invention, the generator is electrically connected and, therefore, connected with the existing electrical vehicle wiring only after a defined time period. According to an alternative embodiment, a generator voltage, which is below the vehicle voltage, is generated in the first time period.
Finally, in another embodiment, a mechanical uncoupling of the generator from the internal-combustion engine may occur during the first time period, so that the generator is no longer driven at all. Although, by means of this approach, the frictional losses in the generator can also be avoided, increased constructive expenditures must be accepted to perform the uncoupling.
The above-mentioned first time period for the uncoupling may be firmly defined or freely selectable. If the time period is selectable, it may be selected, for example, as a function of vehicle operating conditions, such as exhaust gas data. If it is firmly defined, the generator may be deactivated, for example, for 10 or 20 seconds after the start. Depending on the embodiment of the generator, it is possible that the electrical switching-off (uncoupling) actively takes place by way of a so-called BSD-interface at the generator itself.
In the case of an alternative embodiment, when the voltage produced by the generator is below the vehicle wiring voltage, electrical consuming devices load only the battery and not the generator. Furthermore, the battery is also not charged from the generator. Therefore, no excessive additional load results from the generator operation, so that the internal-combustion engine also does not have to supply any significant power to the generator. If the battery voltage breaks down because of an excessive loading by consuming devices, then the generator can be used as a xe2x80x9cback-upxe2x80x9d, so that the voltage reduction takes place only to the level of the voltage generated by the generator at this point in time.
On the whole, by means of the above-mentioned approaches, the exhaust emission values in the starting range, particularly during the cold start of an internal-combustion engine, can be considerably improved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.